Transbay Transit Center slowly moves toward reopening.
Officials say they’re closing in on cause of girder cracks, and fix
San Francisco’s $2.2 billion Transbay Transit Center, which has been shut down by cracked steel girders for longer than it was open, inched closer Thursday to reopening, but no one was ready to speculate when that might happen.
Transbay officials, consultants and overseers said Thursday that they’ve narrowed in on holes cut into two large support beams with a welding torch as the likely cause of the cracks. They’ve also designed a potential fix — sandwiching the damaged part of the girder between thick steel plates that would be bolted together.
But what everyone wants to know — how long the repairs will take and when the transit hub could reopen — remains a mystery.
The three-block-long, three-story transit center, and its rooftop park, have been closed since the Sept. 25 discovery of two cracked support girders where the South of Market complex crosses Fremont Street. The building has been temporarily braced using hydraulic jacks and huge steel pipes while engineers search for the cause of the cracks and try to determine whether any of the rest of the center is at risk.
Mark Zabaneh, executive director of the Transbay Joint Powers Authority, said he hopes to be able to provide a timeline, and more definitive answers, at the agency’s next board meeting on Jan. 10.
“There are a number of unanswered questions,” he said. “We’re hoping that by the next meeting we will have more clarity on the path forward.”
The authority is proceeding cautiously, and slowly, out of concerns for safety and public confidence, inevitable litigation, and political pressure from San Francisco Mayor London Breed and Oakland Mayor Libby Schaaf. They insisted that the Metropolitan Transportation Commission form an independent panel of engineering experts to review the investigation into the cause, the effectiveness of the repairs and the safety of the center.
Before the authority can declare a cause, approve a
repair strategy or pronounce the rest of the center safe for reopening, those decisions have to be approved by the peer review panel.
Since Tuesday, the panel has been reviewing the results of several tests on large chunks of steel taken from the cracked beams. While the results are preliminary, tests at the LPI metallurgic lab in New York City point toward holes cut with a welding torch leading to the cracking of the 60-foot girders.
Robert Vecchio, the lab’s president, said the tests showed that “thermal cutting” of what are known as welding access holes into the girders caused a layer of bubbles and bumps while cooling that can develop tiny shallow cracks. Those probably contributed to the larger cracks that appear to emanate from the corners of the access holes.
Typically, the uneven layer, known as martensite, is ground down as required by building codes. But the tests found that was not done on the damaged girders, Vecchio said.
Robert Hazleton, president of Herrick Steel, which manufactured the steel girders, disputed the description of the holes as “welding access holes,” saying they were another type of hole, demanded by the transit center’s contractor, and not subject to the same standards.
Fixing the damaged girders is likely to involve attaching thick steel plates above and below the cracked areas, and bolting them together, said Bruce Gibbons, managing partner of Thornton Tomasetti, the transit center’s civil engineer.
The head of the peer review panel, Michael Engelhardt, a civil engineering professor at the University of Texas, Austin, said the group is trying to be thorough and remain independent and at the same time not unnecessarily slowing the process.
“We understand the urgent nature of the situation,” he said. “But people need to have confidence.”
Tests by a metallurgic lab point toward holes cut with a welding torch leading to the cracking.